By Mohammed Ghobari and Mohammed Mukhashaf
CAIRO/ADEN, May 10 (Reuters) - Iranian-allied Houthi fighters in Yemen accepted on Sunday a five-day humanitarian ceasefire proposed by their adversary Saudi Arabia but said they would respond to any violations.
Neighboring Saudi Arabia had said on Friday that the ceasefire could begin on Tuesday if the Houthi militia agreed to the pause, which would let in badly needed food and medical supplies.
Backed by the United States, a Saudi-led coalition has been conducting air strikes against the Houthis and army units loyal to ex-president Ali Abdullah Saleh since March 26 with the aim of restoring the government of President Abd-Rabbu Mansour Hadi.
Colonel Sharaf Luqman, spokesperson for the Houthi-allied army, said on Sunday that Yemeni forces agreed to the truce but would confront any attacks by Hadi loyalists on battlefronts which stretch across much of the impoverished country.
The Houthis say their campaign is aimed at defeating al Qaeda militants based in Yemen and accuse Hadi's forces of supporting the group.
"Any military violation of the ceasefire from al Qaeda and those who stand with it ... will be responded to," Luqman said in a statement published by Saba news agency.
Arab air strikes and heavy shelling on Sunday rocked the southern city of Aden, the epicenter of fighting for more than six weeks, and southern fighters questioned the proposed pause.
"We doubt that the Houthis would stick to a ceasefire or truce because they have repeatedly broken political commitments they have made in the past," a pro-Hadi militiaman in the city told Reuters.
The Houthis' acceptance of a truce came as Saudi ground forces conducted air strikes, fired artillery and launched at least two dozen rockets on Saada province, a Houthi stronghold along its southern border.
Riyadh has called on civilians to evacuate the province, in a move that has drawn criticism from the United Nations.
"The indiscriminate bombing of populated areas, with or without prior warning, is in contravention of international humanitarian law," the U.N. Humanitarian Coordinator for Yemen Johannes van der Klaauw said in a statement.
"Many civilians are effectively trapped in Saada as they are unable to access transport because of the fuel shortage. The targeting of an entire governorate will put countless civilians at risk."
International concern about the humanitarian situation has grown as the strikes have killed more than 1,300 people, sent locals fleeing from their homes and destroyed infrastructure, leading to shortages of food, medicine and fuel.
Iranian news agency Tasnim said an aid ship would set sail for the Houthi-controlled Red Sea port of Hodaida on Sunday, in a move that will likely be blocked by the Saudi-led coalition.
Iran denies arming the Houthis, but the Sunni Muslim monarchies leading the campaign believe Tehran is using the Shi'ite Houthis to gain a foothold in the Arabian Peninsula and have blocked previous aid flights.
Residents in the capital Sanaa reported that Arab planes bombed for a second day in a row the vast compound which is home to ex-president Saleh, a key player in Yemen's political crisis whose loyalists in the army fight on the Houthis' side.
In a sign that the wily political operator was unscathed, Saleh blasted the Saudi-led campaign on his official Twitter account on Sunday.
"Look for a solution to exit from your quagmire of killing and destroying the Yemeni people. Stop drinking Yemeni blood and let us solve our differences," he wrote.
Saleh and the Houthis have asked for a U.N.-backed political dialog, but their opponents say they have yet to make any concessions and have called for them to end their military push on Aden and Yemen's south. (Writing By Noah Browning and Maha El Dahan; Editing by Gareth Jones)